In recent years, active matrix liquid crystal display devices having advantages such as being thin and light, being able to be driven at low voltage, and having low power consumption are widely used as display panels for various electronic devices such mobile devices including mobile phones and portable gaming systems, and laptop computers.
Such an active matrix liquid crystal display device includes a TFT substrate having thin film transistors (hereinafter abbreviated as “TFTs”) as switching elements, and a color filter substrate (hereinafter, “CF substrate”) having colored layers and being bonded as an opposite substrate to the TFT substrate. A liquid crystal layer is provided between the TFT substrate and the CF substrate.
FIG. 20 is a plan view showing a configuration of one pixel on the TFT substrate of such a liquid crystal display device, and FIG. 21 is a cross-sectional view of FIG. 20 along the line E-E.
The TFT substrate 50 includes a glass substrate 60 as an insulating substrate, a plurality of data signal lines 51 (hereinafter, “source lines”) formed on the glass substrate 60, and a plurality of scan signal lines 52 (hereinafter, “gate lines”) intersecting with the source lines 51 to form a grid pattern. The TFT substrate 50 also has a plurality of auxiliary capacitance lines 53 extending in parallel with the plurality of gate lines 52. One pixel is provided at each intersection between the plurality of source lines 51 and gate lines 52.
Each pixel has a TFT 56 as a switching element having a source electrode 54 to which a source line 51 passing through the corresponding intersection is connected, and a gate electrode 55 to which a gate line 52 passing through the corresponding intersection is connected.
An insulating film 62 is formed on the gate electrode 55, the gate line 52, and the auxiliary capacitance line 53, and a drain electrode 64 of the TFT 56 is formed on the insulating film 62. An interlayer insulating film 69 including a protective film 65 and an organic film 68 (planarizing film) provided on the protective film 65 is formed on the drain electrode 64.
A pixel electrode 66 is formed on the interlayer insulating film 69, a contact hole 67 is formed in the interlayer insulating film 69, and a portion of the contact hole 67 contacts the drain electrode 64. The pixel electrode 66 is in contact with the drain electrode 64 in the contact hole 67, and thus, the pixel electrode 66 and the drain electrode 64 are electrically connected to each other (see Patent Document 1, for example).